The specific objectives of the proposed research are to gain an understanding of the functions of the polyoma virion proteins. Special emphasis will be placed in evaluating the possible role the polyoma virion histones may have in regulating the transcription of virus- specific messenger RNAs in productively-infected and in transformed cells. The effect of histones on DNA transcription will be measured by testing the efficiency of the nucleohistone complexes as templates for RNA polymerase in vitro and characterizing and comparing the in vitro RNA products with those synthesized in infected and transformed cells by hybridization experiments. The effects of selective removal of histone components will be analyzed to determine what effects the individual histone classes may play in the restriction of DNA transcription. This system may prove to be an ideal model system for studying the biological function of nucleohistone complexes and assessing the effects of histone modifications, e.g., acetylation, phosphorylation, etc. on histone activity.